1914-15.] Conductivity of Salt-saturated Hydrochloric Acid. 141 
This cell may be filled and washed out while in the bath, and need 
seldom be removed. The liquid in entering it passes through only a 
short length of tube, and has very small opportunity to cool. It is very 
light in construction, and even when filled with liquid colder than the 
surrounding water reaches a constant conductance in from twenty to 
thirty seconds. 
The constant of the cell used for these measurements was about 170. 
The exact figure was found to remain constant within the limits of the 
error of measurement for many weeks. It was determined at intervals 
by means of a sodium chloride solution saturated at 18° (K^go = 0‘216I). 
By slightly modifying the design, other cells having a constant of from 
2'0 to 3*0 were constructed. They differed from the one illustrated in 
having no central narrow tube. The leading tubes and electrodes were 
all sealed into the same compartment, so that the latter were from IJ to 
2J inches apart These cells were found useful for aqueous solution of 
strong electrolytes of about decinormal strength and proved specially 
convenient for work with decinormal solutions of salts in mixtures of 
alcohol and water. 
In case the liquid in the cell is required for chemical analysis it can 
be easily blown out, without removing the cell from the bath, into a 
weighing bottle. This was done in the present case for the estimation 
of the salt. The solution was washed into a platinum dish, evaporated, 
and the salt residue was weighed after heating to dull redness. 
Samples were also taken in the same way for estimation of their acid 
contents. After weighing, they were diluted with water, and a known 
fraction was titrated with decinormal potassium hydroxide, using phenol- 
phthalein, and boiling during titration. The potash solution had been 
titrated against a solution of pure hydrochloric acid. The acid had in turn 
been standardised by a solution of silver nitrate prepared from pure silver, 
using the Gay-Lussac method of dropping the acid into the silver nitrate 
solution until no further cloudiness appeared. The temperature of the 
solutions was kept as nearly constant as possible and all measuring 
apparatus was standardised. 
The results obtained are given in the table. R is the resistance in 
ohms used to balance the cell so that the point of balance was nearly in the 
centre of the slide wire. is the specific conductivity at 18°, in reciprocal 
ohms. Column III gives the percentage of hydrogen chloride, and Column 
IV the percentage of salt, found by analysis in each of the solutions used. 
The figures in Column V were calculated from those in Columns III and 
IV. They give the percentages of hydrogen chloride in those solutions 
